# 1209 Remove All Adjacent Duplicates in String II

You are given a string `s` and an integer `k`, a `k` duplicate removal consists of choosing `k` adjacent and equal letters from `s` and removing them, causing the left and the right side of the deleted substring to concatenate together.

We repeatedly make `k` duplicate removals on `s` until we no longer can.

Return the final string after all such duplicate removals have been made. It is guaranteed that the answer is unique.

Example 1:

``````Input: s = "abcd", k = 2
Output: "abcd"
Explanation: There's nothing to delete.
``````

Example 2:

``````Input: s = "deeedbbcccbdaa", k = 3
Output: "aa"
Explanation:
First delete "eee" and "ccc", get "ddbbbdaa"
Then delete "bbb", get "dddaa"
Finally delete "ddd", get "aa"
``````

Example 3:

``````Input: s = "pbbcggttciiippooaais", k = 2
Output: "ps"
``````

Constraints:

• `1 <= s.length <= 105`
• `2 <= k <= 104`
• `s` only contains lowercase English letters.
 `````` 1 2 3 4 5 6 7 8 9 10 11 `````` ``````class Solution: def removeDuplicates(self, s: str, k: int) -> str: stack = [] # [count, char] for c in s: if not stack or c != stack[-1]: stack.append([1, c]) else: stack[-1] += 1 if stack[-1] == k: stack.pop() return ''.join([char * count for count, char in stack])``````